1. Field of the Invention
The present invention relates to a developing device in an electrophotographic apparatus and particularly relates to an improvement in a developing device of the type having first and second developing rolls which rotate in the same direction.
2. Description of the Related Art
The developing device of this type in an electrophotographic apparatus, having first and second developing rolls rotating in the same direction, is known, for example, from U.S. Pat. No. 4,177,757, etc.
In the developing device of this type, if the rotational speed of the developing rolls is increased to improve the printing speed, a centrifugal force given to a developer on the surface of the developing rolls is increased so that the force by which the developer on the delivering magnetic pole of the second developing roll is thrown out in the direction of a tangential line drawn from the position of the delivering magnetic pole to the side of the direction of rotation of the developing roll is increased. Accordingly, the magnetic field acting between the delivering magnetic pole of the second developing roll and the receiving magnetic pole of the first developing roll is not sufficient to deliver the developer from the second developing roll to the first developing roll. Accordingly, a part of the developer is involved in the direction of the rotation of the first developing roll. There arises a problem in that the developer is jammed not only between the second developing roll and the first developing roll but also between the second developing roll and a photosensitive body so that it becomes impossible to obtain a stable printing quantity or it becomes impossible to rotate the photosensitive body or the developing rolls so that printing cannot be carried out.